Chronic Obstructive Pulmonary Disease

Description

• Third leading cause of death in the U.S.
• A disease characterized by airflow obstruction due to several processes:
  • Emphysema: Irreversible alveolar destruction with loss of airway elastic recoil
    • Represents accelerated aging of the lung
  • Chronic bronchitis: Airway inflammation without alveolar destruction
  • Reactive airway disease: Reversible bronchospasm, mucous plugging, and mucosal edema
• COPD affects ∼10% of the population and 50% of smokers
• Increased incidence of hypertension, diabetes, heart failure, and cardiovascular disease in those with COPD
• Frequent exacerbations lead to:
  • Greater mortality
  • Faster decline in lung function
  • Worse quality of life
  • Increased risk of hospitalization
• Modified Medical Research Council (mMRC) dyspnea scale:
  • Grade 0: Only breathless with strenuous exercise
  • Grade 1: Short of breath when hurrying or walking up a slight hill
  • Grade 2: Walk slower than people of same age due to dyspnea or have to stop for breath when walking on level ground
  • Grade 3: Stop for breath after 100 m on level ground
  • Grade 4: Too breathless to leave the house or breathless when dressing/undressing
• GOLD guidelines:
  • Group A:
    • No more than 1 exacerbation/yr
    • FEV1 >80% predicted
    • mMRC of 0 or 1
  • Group B:
    • mMRC of 2 or more
    • FEV1 50–80% of predicted
  • Group C:
    • mMRC <2
    • ≥2 exacerbations/yr
    • FEV1 30–49% of predicted
  • Group D:
    • High symptom burden
    • mMRC ≥2
    • High risk for exacerbations
    • FEV1 <30% of predicted

Risk Factors

Genetics
α₁-antitrypsin deficiency

Etiology

• Smoking is the overwhelming cause:
  • COPD develops in 15% of smokers
• Air pollution
• Airway hyperresponsiveness
• α₁-antitrypsin deficiency
• Autoimmunity may play a role
• Acute exacerbations:
  • Viral infections:
    • >50% of exacerbations associated with recent cold symptoms
    • Decreased immunity may make the host more susceptible to a COPD exacerbation
    • Rhinovirus
    • Respiratory syncytial virus (RSV)
  • Bacterial infections:
    • Bacteria isolated in 40–60% of sputum during acute exacerbation
    • Most common:
      • Haemophilus influenzae
      • Moraxella catarrhalis
      • Streptococcus pneumoniae
    • More likely if:
      • Increased dyspnea
      • Increased sputum volume
      • Purulent sputum
  • Pollutants:
    • Changes to immunity
    • Increased airway inflammation
  • Seasonal variations:
    • More common and more severe in winter